Field of the Invention
The present invention relates to an insulating coating material and its use, in particular, relates to an insulating coating material having excellent abrasion resistance used for electric wires and cables and the like for aerospace applications.
Description of Background Art
For an insulating coating material for electric wires and cables for aerospace applications, in addition to heat resistance, electrical insulation, chemical resistance and flame resistance, durability characteristics such as abrasion resistance and cut through resistance (cut resistance) are demanded.
For example, as materials for electric wires and the like for aerospace applications, multilayer polyimide-fluoropolymer insulating structures and insulated wires and cables and the like having excellent cut resistance, have been developed (for example, Patent Documents 1-5).
Patent Document 1 relates to a multilayer polyimide fluoropolymer insulating material, and is mainly intended to improve dynamic cut resistance (cut through resistance). As insulating films used in an insulating coating material, specifically, a polyimide copolymer base layer of polyimide that is derived from pyromellitic acid dianhydride and 4,4′-diaminodiphenyl ether and has a thickness of 2 mils or 1 mil, a polyimide copolymer base layer that is derived from 40 mol % of 3,3′,4,4′-biphenyltetracarboxylic acid dianhydride, 60 mol % of pyromellitic acid dianhydride, 60 mol % of p-phenylenediamine, and 40 mol % of 4,4′diaminodiphenyl ether and has a thickness of 0.5 mils, and a polyimide copolymer base layer that is derived from 100 mol % of pyromellitic acid dianhydride, 60 mol % of p-phenylenediamine and 40 mol % of 4,4′diaminodiphenyl ether and has a thickness of 0.75 mils are disclosed. However, there is no specific description about abrasion resistance.
Patent Document 2 is mainly intended to improve heat seal strength, and an Apical AV is used as an insulating film that is used for an insulating coating material. However, there is no description of specific evaluation of abrasion resistance.
Patent Document 3 is intended to also improve abrasion resistance (abrasion wear). However, Patent Document 3 discloses that, when a relatively thin polyimide film having a thickness of 0.65 mils is used, the best abrasion resistance is 111 times.
Patent Document 4 discloses a wire wrapping composition that includes a polyimide layer and a bonding layer of a fluorine resin. According to Patent Document 4, although there is disclosure on a scraping (abrasion) property, the scraping property is not evaluated as a property.
Patent Document 5 discloses a polyimide film that has a specific loop stiffness value and a specific linear expansion coefficient. Patent Document 5 is intended to improve thermal dimensional stability and sliding flexibility, which are properties that are required for a polyimide film used in a flexible printed circuit board. Patent Document 5 discloses a polyimide film for a flexible printed circuit board, in which a polyimide film that is formed from 4,4′-oxydianiline and p-phenylenediamine and has an average linear expansion coefficient of 1.0-2.5×10−5 cm/cm/° C. in a temperature range of 100-200° C. is used at a specific ratio. However, attention is focused on applications and characteristics different from those of an insulating coating material for electric wires and cables, and a structure is also different. Further, a loop stiffness value of 0.4-1.2 g/cm is a relatively low value.
Currently, as insulating coating materials that can be used, An Oasis manufactured by DuPont and an Apical (Type AF) manufactured by Kaneka North America are known.    Patent Document 1: Japanese Patent Laid-Open Publication No. Hei 10-100340 (published on Apr. 21, 1998).    Patent Document 2: U.S. Patent Application Publication No. 2010/0282488.    Patent Document 3: U.S. Pat. No. 7,022,402.    Patent Document 4: Japanese Translation of PCT International Application Publication No. 2013-512535 (published on Apr. 11, 2013).    Patent Document 5; U.S. Pat. No. 7,018,704.